Bi-directional flow thermostat

ABSTRACT

In preferred form a thermostat valve assembly having a sleeve valve member moved by a thermo-sensitive motor from a closed position in which annular valve portions on both ends of the sleeve member are seated against ends of a cup-shaped frame member into an open position in which dual coolant flow paths are provided between the frame member and the outer surface of the sleeve member and through the interior of the sleeve member. The construction of the thermostat lends itself to an in-line assembly method since all parts are installed through the top of the frame member and are concentric with respect to the frame member.

[ 1 Apr. 25, 1972 United States Patent Beatenbough et al.

3,241,760 3/l966 Bailey......................................236/34 [54] BI-DIRECTIONAL FLOW THERMOSTAT [72] Inventors:

Primary Examiner-Edward J. Michael Paul Beatenbough, Medma, John Attorney-W. S. Pettigrew, J. C. Evans and K. H. MacLean, A. Gardner, Jr., Tewksbury, Mass. JL

General Motors Mich.

[ ABSTRACT In preferred form a thermostat valve assembly having a sleeve [73] Assignee: Corporation, Detroit,

valve member moved by a thermo-sensitive motor from a closed position in which annular valve portions on both ends of the sleeve member are seated against ends of a cup-shaped "236/34 frame member into an open position in which dual coolant MFOIP 7/16 flow paths are provided between the frame member and the 136/34 34 5 93 outer surface of the sleeve member and through the interior of the sleeve member. The construction of the thermostat lends 0 w m 7 u n 9 n n 1 H n I 9 u n 4 U n 2 H U m mm h D l N a "Ne M "us I hf 0 .0 m. H. m P mm m n HUN 2 2 555 rt .1 [.ll.

itself to an in-line assembly method since all parts are installed through the top of the frame member and are concentric with respect to the frame member.

References Cited UNITED STATES PATENTS 3,189,276 Bailey......................................236/34 4Claims, 15 Drawing Figures P'ATENTEDAPR 2 5 I972 SHEEI 10F 3 A T TORNEY PATENTEUAPR 25 W2 3, 658 243 sum 3 UF 3 A77 RNEY BI-DIRECTIONAL FLOW TI'IERMOSTAT This invention relates to a thermostat valve particularly for use in a conduit of an automobile cooling system and the valves assembly process.

Poppet and butterfly type thermostate valve assemblies have previously been used to regulate coolant flow through conduits in an internal combustion engine. When an automotive internal combustion engine is operated at relatively high speeds, it is desirable to pass large quantities of coolant through the engine for cooling. Both the poppet and the butterfly type valves offer considerable resistance to coolant flow when open. In contrast, the present sleeve valve thermostate permits a large quantity of coolant to flow relatively unrestricted through the sleeve valve s interior.

Previous thermostate sleeve valve assemblies support a movable or reciprocal sleeve member within a frame. An annular sealing member is supported on the frame to block fluid flow between the frame and the outer surface of the sleeve member. As the sleeve member moves with respect to the seal in response to temperature changes of the ambient coolant,

the seal rubs against the sleeve. In this way the seal is worn and fluid leakage occurs. This uncontrolled coolant leakage is undesirable and increases the engine warm-up period.

The present thermostate sleeve valve includes a cup-shaped frame member having an open end which defines a fluid outlet and inlet openings through its cylindrical side surface. A cylindrical sleeve valve is supported within the frames interior and includes annular valve portions on its ends which simultaneously seat against the bottom and top surfaces of the frame member. A coil spring around the sleeve valve normally maintains the sleeve valve in its closed position. A thermo-sensitive motor supported by the bottom of the frame member moves the sleeve valve away from the bottom ofthe frame member in response to increasing coolant temperature surrounding the motor. This movement unseats the annular valve portions .from the bottom and top of the frame member to open dual coolant flow paths over the outer surface and through the interior of the sleeve valve. By mounting valve elements on the sleeve valve, frictional movement between a seal and the movable sleeve valve is eliminated. Consequently, seal wear and the associated leakage problem will not occur.

The present thermostate sleeve valve provides increased coolant flow in response to vehicle speed as sensed by coolant pressure. A large coolant flow through the thermostate is desirable at high engine speeds to limit engine metal temperatures and control fuel mixture temperatures. Control of these factors is important because of the greatly increased rate of heat flow from the combustion gases in the engine at high speeds. The present thermostate sleeve valve has a differential in diameters of the valve portions which produces a differential valve area. Once the sleeve valve is moved to an open position by the thermal motor, dynamic pressure of the coolant acts against this differential valve area to further move the sleeve valve to a more open position and increase coolant flow through the thermostat. This pressure force by the coolant is a combination of the effect of coolant velocity and coolant static pressure.

Therefore, an object of the invention is the provision of a thermostat valve assembly having a sleeve valve member reciprocal in a frame member with annular valve portions on the ends of the sleeve member which contact the frame to block coolant flow when the sleeve valve is in a closed position and which move from the sleeve valve out when the sleeve valve member is in an open position to control coolant flow past the valve portions.

A further object of the invention is the provision of a thermostat valve assembly having a sleeve valve member reciprocal in a frame member to control coolant flow through the interior of the sleeve valve and through the annular space between the frame member and the sleeves outer surface.

A still further object of the invention is the provision of a thermostat valve assembly having a sleeve valve which is reciprocal within a frame member and which has annular valve portions on its ends of differing diameters which produce an area differential on which coolant pressure acts to move the sleeve valve into a more open position.

A still further object of the invention is the provision of a convenient and economical method of assembling the sleevetype thermostat by an in-line method of assembly.

Further objects and advantages of the present invention will be apparent from the following detailed description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

IN THE DRAWINGS:

FIG. I is a fragmentary side view of an internal combustion engine and an automobile radiator partially broken away to reveal the subject thermostat valve assembly;

FIG. 2 is a vertical sectioned view of the thermostat valve assembly in its closed position;

FIG. 3 is a vertical sectioned view of the thermostat valve assembly in its partially opened position;

FIG. 4 is a vertical sectioned view of the thermostat valve assembly in its fully open position;

FIG. 5 is a perspective view of the sleeve valve shown in FIGS. 2 4 which is partially broken away to reveal its interior;

FIG. 6 is a vertical side view of another embodiment of the subject thermostat valve assembly;

FIG. 7 is a vertical sectioned view of the thermostat valve assembly shown in FIG. 6 taken along sectional line 77 looking in the direction of the arrows;

FIG. 8 is a horizontal top view of the thermostat valve assembly shown in FIG. 6 taken along reference line 14-14 and looking in the direction of the arrows;

FIG. 9 is a vertical sectioned view of another embodiment of the thermostat valve assembly similar to the assembly shown in FIG. 7;

FIGS. 10 are vertical views of the thermostat valve assembly revealing the assembly process of the thermostat.

A partial view of the front portion of an automobile internal combustion engine 10 is shown in FIG. 1. The engine 10 supports a fan 12 and a coolant pump generally shown by the numeral 14. Pump 14 includes an inlet 16 connected by a hose 18 to an outlet 20 of a radiator 22. The pump 14 passes water or other coolant through water passages within the engine 10 and into an outlet 24. The coolant flows from outlet 24 through a hose 26 into the upper portion of radiator 22. C00- lant flow is regulated by thermostat valve assembly 28 in outlet 24 in response to coolant temperature.

The thermostat valve assembly 28 is illustrated in more detail in FIGS. 2 4. In these figures, a cup-shaped frame member 30 is supported within the outlet 24 by a radially outwardly extending annular flange 32 which is secured between outlet members 34 and 36 by screws 38. The flange 32 defines an outlet 40 in valve assembly 28. Inlet openings 42 extend through the cylindrical wall of the frame member 30.

A hollow cylindrical sleeve valve 44 is supported within the interior of the cup-shaped frame member 30. The sleeve valve 44 has a radially outwardly extending annular valve portion 46 on its lower end. Valve portion 46 contacts the bottom 48 of the frame member 30 when the sleeve valve 44 is in a closed position as shown in FIG. 2. Another valve portion 50 extends radially outwardly from the sleeve valves upper end. An annular sealing ring 52 is located adjacent valve portion 50 around the sleeve valve 44. When the sleeve valve 44 is in a closed position as shown in FIG. 2, coolant flow is prevented by the contact of valve portion 46 and the bottom 48 of frame 30 and of sealing ring 52 and the outlet portion 40 of frame 30. The sleeve valve 44 is biaseddownward against the bottom 48 of frame 30 by a coil spring 54 which is compressed between valve portion 46 and tabs 56 on the frame member 30.

The valve assembly 28 is opened, as shown in FIGS. 3 and 4, by a thermo-sensitive motor 58 supported by the bottom 48 of frame, 30. The motor 58 includes an outer casing or shell 60 which surrounds atemperature sensitive wax 62, a compressible diaphragm 64. and an extensible member or plunger 66. As

the wax expands in response to increased temperature, the diaphragm 64 is compressed which forces the plunger 66 outward from the motor 58. A seal 68 encircles plunger 66 and prevents the escape of wax.

The free end of plunger 66 contacts and exerts an upward force against an internal web 70 of the sleeve valve 44. As shown in FIG. 5, web 70 includes a central portion 72 and a plurality of radially extending arms 74 which are joined to the cylindrical surface of the sleeve valve. The upward force of plunger 66 against the web 70 causes the sleeve valve 44 to move upward. This causes the valve portions 46 and 50 to move away from frame member 30 which opens dual coolant flow paths through the valve assembly 28. One flow path 75 extends between frame member 30 and the valve portion 50 of sleeve member 44. The other flow path 77 extends between valve portion 46 and the bottom 48 of the frame 30 and hence through the internal flow passage 76 in the sleeve valve 44.

A desirable feature of the subject valve assembly is illustrated in FIG. 3. When the valve assembly is initially opened, a flow metering action through the valve occurs between valve portion 46 and the frame sides. The sleeve valve 44 must move a predetermined distance before coolant flow is appreciably increased through flow path 77. In the event that less metering is desired, the annular flow space between valve portion 46 and the cylindrical surface of frame 30 may be increased. Conversely, this flow area may be decreased to produce more metering. Also the location of inlets 42 may be vertically moved to control metering.

Another desirable feature of the subject valve assembly arises because of the dual valving action by portions 46 and 50. When the thermostat opens, valve portion 50 and sealing ring 52 move upward with the sleeve valve 44 away from frame member 30. In prior sleeve-type thermostats, a seal around the upper end of the sleeve member is supported by the frame and is subjected to movement ofthe sleeve. This can result in undesirable wear of the seal. The valve seal 52 in the subject sleeve-type thermostat does not rub against the sleeve valve 44 or frame 30 as the thermostat opens. Consequently, there is little wear of valve parts. In addition, the resiliency of the seal 56 minimizes the need for a precise tolerance between the upper and lower valve portions.

Another advantage of the subject valve assembly lies in its flexibility to produce variable operating characteristics. It is usually desirable in automotive engine cooling to open the thermostat valve assembly more when the engine is running at high speed than when the engine is running at low speed. This is because the engine cooling requirements are tied to the mass heat flow from the ignited fuel mixture to the engine block. By providing a larger upper valve diameter than the lower valve diameter, the pressure of coolant acts upon the resultant differential valve area to cause the valve assembly to assume a more open position. For example, with a 1.54 inch diameter of outlet 40 and a 1.50 inch diameter of the valve portion 46, there is a differential area of 0.094 square inches. The hydrostatic pressure exerted on this differential area acts to open the valve. Normally, a sufficiently stiff coil spring 54 is selected to maintain the valve closed under normal pump output pressures whenever the coolant temperature is below the thermostat's start-to-open temperature. Once the temperature of coolant reaches the start-to-open temperature and the sleeve valve 44 opens however, the effect of coolant flow on the differential area produces a force on the valve which is additive to the force of the thermal motor 58. This force influences the position of the sleeve valve to produce a greater opening and greater fluid flow than would otherwise occur. Consequently, the speed of the engine which is directly related to pump pressure partially controls the thermostat flow rate.

The location of the coil spring 54 contributes to increased coolant flow through the thermostat 28 as coolant temperature increases. As sleeve valve 44 moves to its fully opened position, which is shown in FIG. 4, spring 54 is not in line with the main flow path 77.

The valve portions 46 and 50 on the sleeve valve 44 shown in FIGS. 2 4 are an integral part of the sleeve valve which is of plastic material. Other embodiments of the subject thermostat valve assembly having the same desirable characteristics as the aforedescribed valve are shown in FIGS. 6 11. The valve assembly 78, shown in FIGS. 6 8, has a one-piece cupshaped frame member 80, a radially outwardly directed flange 82, a plurality ofinlet openings 84, an outlet 86, a sleeve valve 88 and a thermal sensitive motor 90. The sleeve valve 88 has an annular metal valve portion 92 press fit over its lower end and an annular metal valve portion 94 press fit over its upper end. The valves 92 and 94 have very small slits as best seen in FIG. 8, which allow for some tolerance variation in the diameter of the sleeve valve 88 while still permitting a desirable interference fit. The upper valve 94 is axially deflectable to a limited degree for minimizing the necessity for a precise tolerance between valves 94 and 92.

In FIG. 9 a thermostat valve assembly 102 is illustrated which is quite similar to the thermostat valve assembly shown in FIGS. 6 8. It includes a frame member 104, having a flange portion 106, inlet openings 108, an outlet opening 110, a sleeve valve 112 and a thermo-sensitive motor 114. Upper and lower metal valves 116 and 118 are press fit upon the ends of the sleeve valve 112 to contact the frame member 104 for controlling coolant flow through the valve assembly 102. A coil spring 120 extends between valve 118 and tabs 122 on frame 104. The upper annular valve 116 differs from valve 94 in that it projects axially downward a limited degree into outlet offrame 104.

The thermostat valve assembly in FIGS. 2 4 is readily assembled by in-line assembly methods. The assembly steps for this thermostat valve assembly are set forth in FIGS. 10 15. With reference to FIG. 10, the hollow, cup-shaped frame member 30 is supported upon a horizontal surface supporting the thermo-sensitive motor 58 within a central opening in the bottom 48 of the frame member. The open end of the frame member forms the valves outlet 40 and provides the opening through which the remaining parts of the valve assembly are installed in a subsequent in-line assembly operation. In FIG. 11, a sleeve valve 44 with the lower valve portion 46 is inserted into the interior ofthe frame member 30 which permits the valve portion 46 to rest against the frame bottom 48. In this position, the plunger 66 of the motor 58 contacts the web 70 of sleeve valve 44. Subsequently, as shown in FIG. 12, the coil spring 54 is slipped over and around the cylindrical sleeve valve 44 until the lower end of the coil spring 54 rests against valve portion 46. Subsequently, as shown in FIG. 13, the coil spring 54 is compressed to a predetermined length and tabs 56 on frame 30 are bent radially inward to retain the coil spring when it is released. An annular sealing ring 52 is then applied around the upper end of the sleeve valve 44 to contact the frame member 30 at outlet 40. The final step in assembling the valve assembly is shown in FIG. 15 and includes folding or spinning the upper edge of valve 44 radially outward to form valve portion 50 which covers the sealing ring 52. This final spinning step retains the sealing ring 52in sealing engagement with the frame 30.

After assembly by the formation of valve portion 50, the lower end of the thermo-sensitive motor 58 may then be distorted to calibrate the thermostat valve assembly to a predetermined start-to-open temperature.

It should be obvious that the valve assembly shown in FIGS. 7 9 could be assembled in essentially the same manner shown in FIGS. 10 15. However, a cylindrical sleeve valve having a lower metal valve in place is substituted for the sleeve with an integral lower valve and an upper metal valve is pressed over the upper end of the sleeve member to form the upper sealing in place ofa spinning or folding operation.

While the embodiments of the present invention as herein described constitute preferred forms, it is to be understood that other forms may be adapted.

What is claimed is as follows:

l. A thermostat valve assembly for regulating fluid flow in a liquid cooling system of an automobile internal combustion engine comprising: a thin walled cup-shaped frame member having a bottom surface, a generally cylindrical side surface and an open end defining a fluid outlet; said side surface having fluid inlets therethrough into the interior of said frame member; an annular flange on the open end of said frame member for supporting said thermostat assembly; a cylindrical sleeve valve supported in the interior of said frame member including an axial flow passage therethrough and annular valve portions extending radially outward from its opposite ends; the first of said valve portions contacting said frame bottom to block fluid flow through said axial flow passage when said sleeve valve is in a closed position; the second of said valve portions contacting an annular portion of said side surface adjacent said fluid outlet to block fluid flow between said frame member and said sleeve valve when said sleeve valve is in a closed position; a coil spring between said sleeve valve and said frame member for normally biasing said sleeve valve into its closed position; a thermo-sensitive motor supported by said frame bottom in heat transfer contact with engine cooling fluid; said thermo-sensitive motor having an extensible member alternately movable inward and outward from said motor in response to decreasing and increasing temperature respectively of engine cooling fluid; said extensible member and said sleeve valve operably connected to produce sleeve valve movement against the force of said coil spring which unseats said valve portions and unblocks dual flow paths through said axial flow passage in said sleeve valve and between said frame member and said sleeve valve in response to a predetermined start-to-open temperature of engine cooling fluid.

2. A thermostat valve assembly for regulating fluid flow in a liquid cooling system of an automobile internal combustion engine comprising; a thin walled cup-shaped frame member having a bottom surface, a generally cylindrical side surface and an open end defining a fluid outlet; said side surface having fluid inlets therethrough into the interior of said frame member; an annular flange on the open end of said frame member for supporting said thermostat assembly; a cylindrical sleeve valve supported in the interior ofsaid frame member including an axial flow passage therethrough and annular valve portions extending radially outward from its opposite ends; the first of said valve portions contacting said frame bottom to block fluid flow through said axial flow passage when said sleeve valve is in a closed position; the second of said valve portions contacting an annular portion of said side surface adjacent said fluid outlet to block fluid flow between said frame member and said sleeve valve when said sleeve valve is in a closed position; a coil spring between said sleeve valve and said frame member for normally biasing said sleeve valve into its closed position; a thermo-sensitive motor supported by said frame bottom in heat transfer contact with engine cooling fluid; said thermo-sensitive motor having an extensible member alternately movable inward and outward from said motor in response to decreasing and increasing temperature respectively of engine cooling fluid; said extensible member and said sleeve valve operably connected to produce sleeve valve movement against the force of said coil spring which unseats said valve portions and unblocks dual flow paths through said axial flow passage in said sleeve valve and between said frame member and said sleeve valve in response to a predetermined start-to-open temperature of engine cooling fluid; said second valve portion having a larger annular valve area exposed to fluid flow than said first valve portion and whereby fluid pressure forces on the differential valve area influence said sleeve valve to an open position.

3. A thermostat valve assembly for regulating fluid flow in a liquid cooling system of an automobile internal combustion engine comprising: a thin walled cup-shaped frame member having a bottom surface, a generally cylindrical side surface and an open end defining a fluid outlet; said side surface having fluid inlets therethrough into the interior of said frame member; an annular flange on the open end of said frame member for supporting said thermostat assembly; a cylindrical sleeve valve supported in the interior of said frame member including an axial flow passage therethrough; annular metal valve elements around the outer surface of said sleeve valve and extending radially outward therefrom; the first of said valve elements contacting said frame bottom to block fluid flow through said axial flow passage when said sleeve valve is in a closed position; the second of said valve positions contacting an annular portion of said side surface adjacent said fluid outlet to block fluid flow between said frame member and said sleeve valve when said sleeve valve is in a closed position; a thermo-sensitive motor supported by said frame bottom in heat transfer contact with engine cooling fluid; said thermosensitive motor having an extensible member alternately movable inward and outward from said motor in response to decreasing and increasing temperature respectively of engine cooling fluid; said extensible member and said sleeve valve operably connected to produce sleeve valve movement against the force of said coil spring which unseats said valve elements and unblocks dual flow paths through said axial flow passage in said sleeve valve and between said frame member and said sleeve valve in response to a predetermined start-toopen temperature of engine cooling fluid.

4. A method for assembling a thermostat valve assembly of the type including a cylindrical sleeve valve supported for reciprocation within the interior of a cup-shaped frame member by a coil spring between the frame member and the sleeve valve and powered by a thermo-sensitive motor comprising the steps of: supporting a cup-shaped frame member on a horizontal surface with its open end directed upward; inserting a thermo-sensitive motor through the open frame end into an opening in the frame bottom with the motors extensible member extending upward; inserting a cylindrical sleeve valve having an annular valve portion on one of its ends through the open frame end until the valve portion rests on the frame bottom; placing a coil spring through the open frame end around the sleeve valve so that its lower end rests on the annular valve portion; compressing the coil spring to a predetermined length below the frame opening; bending tabs on the frame radially inward over the upper end of the coil spring to maintain it in a compressed condition; applying an annular seal around the sleeve valve and against the open end of the frame member; folding the upper edge of the sleeve valve radially outward over the annular seal to form another valve portion on said sleeve valve. 

1. A thermostat valve assembly for regulating fluid flow in a liquid cooling system of an automobile internal combustion engine comprising: a thin walled cup-shaped frame member having a bottom surface, a generally cylindrical side surface and an open end defining a fluid outlet; said side surface having fluid inlets therethrough into the interior of said frame member; an annular flange on the open end of said frame member for supporting said thermostat assembly; a cylindrical sleeve valve supported in the interior of said frame member including an axial flow passage therethrough and annular valve portions extending radially outward from its opposite ends; the first of said valve portions contacting said frame bottom to block fluid flow through said axial flow passage when said sleeve valve is in a closed position; the second of said valve portions contacting an annular portion of said side surface adjacent said fluid outlet to block fluid flow between said frame member and said sleeve valve when said sleeve valve is in a closed position; a coil spring between said sleeve valve and said frame member for normally biasing said sleeve valve into its closed position; a thermo-sensitive motor supported by said frame bottom in heat transfer contact with engine cooling fluid; said thermo-sensitive motor having an extensible member alternately movable inward and outward from said motor in response to decreasing and increasing temperature respectively of engine cooling fluid; said extensible member and said sleeve valve operably connected to produce sleeve valve movement against the force of said coil spring which unseats said valve portions and unblocks dual flow paths through said axial flow passage in said sleeve valve and between said frame member and said sleeve valve in response to a predetermined start-toopen temperature of engine cooling fluid.
 2. A thermostat valve assembly for regulating fluid floW in a liquid cooling system of an automobile internal combustion engine comprising; a thin walled cup-shaped frame member having a bottom surface, a generally cylindrical side surface and an open end defining a fluid outlet; said side surface having fluid inlets therethrough into the interior of said frame member; an annular flange on the open end of said frame member for supporting said thermostat assembly; a cylindrical sleeve valve supported in the interior of said frame member including an axial flow passage therethrough and annular valve portions extending radially outward from its opposite ends; the first of said valve portions contacting said frame bottom to block fluid flow through said axial flow passage when said sleeve valve is in a closed position; the second of said valve portions contacting an annular portion of said side surface adjacent said fluid outlet to block fluid flow between said frame member and said sleeve valve when said sleeve valve is in a closed position; a coil spring between said sleeve valve and said frame member for normally biasing said sleeve valve into its closed position; a thermo-sensitive motor supported by said frame bottom in heat transfer contact with engine cooling fluid; said thermo-sensitive motor having an extensible member alternately movable inward and outward from said motor in response to decreasing and increasing temperature respectively of engine cooling fluid; said extensible member and said sleeve valve operably connected to produce sleeve valve movement against the force of said coil spring which unseats said valve portions and unblocks dual flow paths through said axial flow passage in said sleeve valve and between said frame member and said sleeve valve in response to a predetermined start-to-open temperature of engine cooling fluid; said second valve portion having a larger annular valve area exposed to fluid flow than said first valve portion and whereby fluid pressure forces on the differential valve area influence said sleeve valve to an open position.
 3. A thermostat valve assembly for regulating fluid flow in a liquid cooling system of an automobile internal combustion engine comprising: a thin walled cup-shaped frame member having a bottom surface, a generally cylindrical side surface and an open end defining a fluid outlet; said side surface having fluid inlets therethrough into the interior of said frame member; an annular flange on the open end of said frame member for supporting said thermostat assembly; a cylindrical sleeve valve supported in the interior of said frame member including an axial flow passage therethrough; annular metal valve elements around the outer surface of said sleeve valve and extending radially outward therefrom; the first of said valve elements contacting said frame bottom to block fluid flow through said axial flow passage when said sleeve valve is in a closed position; the second of said valve positions contacting an annular portion of said side surface adjacent said fluid outlet to block fluid flow between said frame member and said sleeve valve when said sleeve valve is in a closed position; a thermo-sensitive motor supported by said frame bottom in heat transfer contact with engine cooling fluid; said thermo-sensitive motor having an extensible member alternately movable inward and outward from said motor in response to decreasing and increasing temperature respectively of engine cooling fluid; said extensible member and said sleeve valve operably connected to produce sleeve valve movement against the force of said coil spring which unseats said valve elements and unblocks dual flow paths through said axial flow passage in said sleeve valve and between said frame member and said sleeve valve in response to a predetermined start-to-open temperature of engine cooling fluid.
 4. A method for assembling a thermostat valve assembly of the type including a cylindrical sleeve valve supported for reciprocation within the interior of a cup-shaped frame member by a coil sprinG between the frame member and the sleeve valve and powered by a thermo-sensitive motor comprising the steps of: supporting a cup-shaped frame member on a horizontal surface with its open end directed upward; inserting a thermo-sensitive motor through the open frame end into an opening in the frame bottom with the motor''s extensible member extending upward; inserting a cylindrical sleeve valve having an annular valve portion on one of its ends through the open frame end until the valve portion rests on the frame bottom; placing a coil spring through the open frame end around the sleeve valve so that its lower end rests on the annular valve portion; compressing the coil spring to a predetermined length below the frame opening; bending tabs on the frame radially inward over the upper end of the coil spring to maintain it in a compressed condition; applying an annular seal around the sleeve valve and against the open end of the frame member; folding the upper edge of the sleeve valve radially outward over the annular seal to form another valve portion on said sleeve valve. 